1. Field of the Invention
The present invention relates to engine-driven systems in which the engine is required to perform a plurality of work functions, and in particular, to such systems in which the work functions are selectively coupled to the engine in order to increase overall system efficiency.
2. Description of the Prior Art
Automobile engines presently are required to operate a variety of accessories as secondary work functions, as well as to perform the primary work function of motivating the vehicle. The secondary work functions include battery charging, air conditioner compressor drive and operation of pollution control equipment, to name but a few. As is well known, each additional secondary work function reduces the amount of power that can be devoted to the primary work function of driving the vehicle, an efficiency reduction which is ultimately manifested in larger fuel requirements per unit distance the vehicle travels.
There have been suggestions in the prior art for removing the load of some of the vehicle accessories only during periods when the vehicle requires additional power for rapid acceleration. Haroldson, in U.S. Pat. No. 3,462,964, discloses a system employing a manifold vacuum switch adapted to switch off the load represented by an automobile air conditioner compressor only during periods of rapid acceleration Kaye, in U.S. Pat. No. 3,602,005, discloses a similar arrangement also employing means coupled to the spark advance. Another arrangement is disclosed in U.S. Pat. No. 3,186,184 to Pruitt. See also the following U.S. Pat. Nos. 2,107,341 to Peo; 2,268,667 to Mendez; 2,929,226 to Baker et al.; and 3,121,314 to Koyanagi.